Glazing with variable optical and/or energetic properties

ABSTRACT

A glazing is described, which includes at least one active layer and at least one reflecting coating on the active layer. A pane, partition, mirror, or door is also described that includes the glazing. A method for making is also described. The glazing exhibits superior thermal and radiative durability, and is capable of modulating the optical appearance of the active layer.

This application is a Continuation of application Ser. No. 08/916,234filed on Aug. 22, 1997, now U.S. Pat. No. 6,055,088.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to glazings with variableoptical/energetic properties. It relates more precisely to glazingswhose characteristics can be modified, for example, under the effect ofan electrical supply, for example, light diffusion or the transmissionwithin some wavelengths of the electromagnetic spectrum, especially inthe infrared and/or in the visible, or under the effect of a particularradiation.

2. Discussion of the Background

An increasingly growing demand exists for so-called “intelligent”glazings, or glazings whose properties can be modulated at will, inorder to take various changing parameters into account. It is highlyadvantageous to be able to control the input of sunlight throughglazings fitted externally in buildings, motor vehicles, or trains, inorder to avoid excessive heating of the rooms or compartments in theevent of strong sunshine. Similarly, it may be useful to control thedegree of vision through glazings, for example in the case of glazingsemployed as internal partitions between two rooms, in a building, orbetween two compartments in a train or an aircraft. Many otherapplications also exist for such glazings: for example, rearview mirrorsin vehicles which, by becoming darker when required, can preventdazzling of the driver, or road or urban sign panels displaying mileagesor designs only intermittently in order to attract attention better.

The interest in such glazings accounts for the fact that many suchsystems have already been studied.

One of the known systems that make it possible to modulate the lighttransmission or absorption of glazings are especially the so-calledviologen systems like those described in U.S. Pat. No. 5,239,406 or inPatent EP-A-0 612 826. The latter makes it possible to obtain a variableabsorption essentially in the visible range.

For the same purpose there are also the so-called electrochromicsystems, which include a layer of an electrochromic material capable ofreversibly and simultaneously inserting cations and electrons, and whoseoxidation states corresponding to the inserted and disinserted stateshave different colors, one of the states exhibiting a higher lighttransmission than the other. The insertion or disinsertion reaction indriven by a suitable electric supply with the aid of a current generatoror a voltage generator. The electrochromic material, usually tungstenoxide-based, is placed in contact with a source of electrons, such as atransparent electrically conductive layer, and a source of cations, suchas an ionically conductive electrolyte.

To ensure at least about a hundred switchings, the layer ofelectrochromic material must be combined with a counterelectrode, itselfalso capable of reversibly inserting cations, symmetrically in relationto the layer of electro-chromic material, so that, macroscopically, theelectrolyte appears to be a simple medium for the cations.

The counterelectrode must consist of a layer which is either neutral incolor, transparent, or weakly colored when the electrochromic layer isin the faded state. Since tungsten oxide is a cathodic electrochromicmaterial, that is to say its colored state corresponds to the mostreduced state, an anodic electrochromic material such as nickel oxide oriridium oxide is generally employed for the counterelectrode. It hasalso been proposed to employ a material which is optically neutral inthe oxidation states involved, such as, for example, curium oxide, ororganic materials like electronically conductive polymers (polyaniline,etc.) or Prussian blue.

The description of such systems will be found, for example, in EuropeanPatents EP-0 338 876, EP-0 408 427, EP-0 575 207 and EP-0 628 849.

At present these systems can be classified into two categories,according to the electrolyte type employed:

1. either the electrolyte is in the form of a polymer or of a gel, forexample a proton-conducting polymer like those described in EuropeanPatents EP-0 253 713 and EP-0 670346 or a polymer conducting lithiumions, such as those described in Patents EP-0 382 623, EP-0 518 754 andEP-0 532 408; or

2. the electrolyte is an inorganic layer, ionically conductive butelectronically insulating; “all-solid” electrochromic systems is theterm which is then employed. For the description of an “all-solid”electrochromic system reference may be made to French Patent ApplicationFR-96/03799 filed on Mar. 27, 1996.

These systems containing reversible-insertion material(s) areparticularly advantageous in the sense that they allow the absorption tobe modulated in a wider range of wavelengths than the viologen systems;they can absorb in a variable manner not only in the visible but also inthe infrared, and this enables them to assume an efficacious opticaland/or thermal function.

The viologenic or electrochromic systems deposited or combined withtransparent substrates form glazings whose light absorption andtransmission (as well as the energy transmission) can vary within givenranges. The ranges are typically determined by the choice of theelectrochromic materials employed and/or their thickness.

Another type of “intelligent” glazing includes what is referred to bythe term of optical valve: this is a film including a matrix ofgenerally crosslinked polymer(s) in which are dispersed microdropletscontaining particles which can orient in a preferred direction under theaction of an electric or magnetic field.

The above film exhibits variable optical properties as a function of theelectrical potential applied to the terminals of the conductive layersplaced on both sides of the film and of the concentration and the natureof the orientable particles.

Thus, Patent WO-93/09460 discloses an optical valve based on a filmincluding a matrix made of crosslinkable polyorganosilane and inorganicor organic orientable particles, more particularly light-absorbingparticles such as polyiodide particles. When a voltage is applied to thefilm, the particles intercept the light much less than when there is novoltage.

A glazing which operates on a similar principle is also known under theterm of liquid-crystal glazing. It is based on the use of a film placedbetween two conductive layers and based on a polymeric material in whichare dispersed droplets of liquid crystals, especially nematic withpositive dielectric anisotropy. When a voltage is applied to the filmthe liquid crystals orient themselves along a preferred axis, and thispermits vision. With no voltage, in the absence of alignment of thecrystals, the film becomes diffusing and prevents vision.

Examples of such films are described in European Patent EP-0 238 164 andU.S. Patents U.S. Pat. No. 4,435,047, U.S. Pat. No. 4.806,922 and U.S.Pat. No. 4,732,456. Films of this type, once laminated and incorporatedbetween two glass substrates, are marketed by Saint-Gobain Vitrage underthe trade name “Priva-lite”.

All the liquid-crystal devices known under the terms of “NCAP” (NematicCurvilinearly Aligned Phases) or “PDLC” (Polymer Dispersed LiquidCrystal) can in fact be employed.

It is also possible to employ, for example, gels based on cholestericliquid crystals containing a small quantity of crosslinked polymer, likethose described in Patent WO-92/19695.

So-called photochromic glazings also exist in which the property ofabsorption in the visible and possibly in at least a portion of theinfrared can be modulated under the effect of energetic radiation,generally situated in the ultraviolet. There are mainly two classes ofthese; the first employs silver salts, especially silver halides, as theactive components, for example, in a glassy matrix, halides which byabsorption in the ultraviolet are converted reversibly into a form ofmetal aggregates. The second class employs as the active componentsorganic dyes that are generally dispersed in a polymer matrix,especially compounds derived from spiroxazines and spiropyrans. Thesecompounds are isomerized reversibly by absorption in the ultraviolet.

However, all of the above glazings exhibit intrinsic limits with respectto their thermal behavior and to their optical appearance.

In fact, these glazings, mentioned above, include a plurality ofelectrically and/or electrochemically active components whose durabilitycan depend on the temperature to which they are subjected. In theparticular case of the glazings with variable light transmission, suchas electrochromic glazings, when they are in the colored state they arehighly absorbent with regard to energy. Thus, when they are employed asexternal glazings, and even more so if they are fitted inclined inrelation to the vertical (which is the case with motor vehicle glazingssuch as car roofs or glazings for building roofing), they can, in thecolored state, heat up to high temperatures reaching 80° C. when exposedfor long enough to strong sunshine. Such temperatures can cause ashortening of the lifetime of the glazings by progressive irreversibledegradation of one or other of their electrochemical components.

The same type of problem can also arise in the case of glazings withvariable light diffusion, like liquid-crystal glazings. Firstly, beyonda certain temperature, called the clearing point, the liquid-crystalpolymer composite, converted to a diffusing state, can spontaneouslyrevert to the transparent state. Subsequently, if a dichroic dye hasbeen added to the composite in order to make it possible to modulateboth the light diffusion and transmission of the glazing, this type ofdye exhibits some degree of instability in the ultraviolet region, aninstability that increases with temperature.

Photochromic glazings also have a disadvantage linked with theirheating. In fact, the two classes of photochromic glazings referred toabove become tinted under the effect of ultraviolet light: an “unstable”state. The return to the faded, “stable” state is obtained by a processwhich is heat activated. Under the effect of ultraviolet light theseglazings take on color, become absorbent and therefore heat up. Instrong sunshine the heating becomes excessive and tends to make theglazings revert to their faded stable state, and the “available”contrast decreases.

Furthermore, the optical appearance of the above glazings may not befully satisfactory, depending on the intended applications. Thus, when awhole facade of a building is fitted with electrochromic glazing, itgives an overall appearance which is somewhat somber when all of it isin the colored state. It could also be advantageous to adjust thereflection appearance of an electrochromic glazing on a car according tothe color of the external bodywork. Similarly, in the diffusing state,glazings containing liquid crystals offer a milky white appearance (inthe absence of dye) which is identical regardless of the side on which aviewer is placed. Thus, it could be advantageous to be able to do awaywith this symmetry of appearance for aesthetic reasons.

Thus, there is a need for new glazings with variable optical and/orenergetic properties that overcome these disadvantages and are capableof being controlled electrically or photochrorically, which exhibit agreater thermal durability and/or whose optical appearance can bemodulated to a greater extent. SUMMARY OF THE INVENTION

The first object of the present invention is to provide new glazingswith variable optical and/or energetic properties that overcome theabove disadvantages and are capable of being controlled electrically orphotochromically, which exhibit a greater thermal durability and/orwhose optical appearance can be modulated to a greater extent.

Another object of the present invention is to provide a glazing thatincludes one means of thermal protection for the active variable opticalsystem.

Another object of the present invention is to provide a glazing thatincludes a means to adjust the optical appearance imparted to theglazing by the active variable optical system.

Another object of the present invention is to provide a glazing in whichexcessive heating of the active system is prevented.

Another object of the present invention is to provide an “intelligent”glazing that can be fitted externally to buildings or vehicles and canbe exposed to long periods of sunshine.

Another object of the present invention is to provide a glazing in whichthe photochromic properties have an extended lifetime, and are notdegraded with excessive heating or exposure to radiation.

Another object of the present invention is to provide an “intelligent”glazing having exceptional durability to visible, ultraviolet, andinfrared radiation.

These and other objects of the present invention have been achieved witha glazing that includes at least one active layer and at least onereflecting coating.

The first embodiment of the present invention therefore relates to aglazing, which includes:

at least one active layer, and at least one reflecting coating on saidactive layer.

The second embodiment of the present invention relates to a pane,partition, mirror, or door, that includes:

a glazing, containing at least one active layer and at least onereflecting coating.

The third embodiment of the invention relates to a method of making aglazing, that includes:

coating at least one reflecting coating onto the surface of an activelayer.

BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various other objects, features and attendant advantages of the presentinvention will be more fully appreciated as the same becomes betterunderstood from the following detailed description of the preferredembodiments, which are not intended to be limiting thereof.

The subject-matter of the invention preferably relates to a glazing thatincludes at least one active layer or system with variable opticaland/or energetic properties, especially electrically controllable of thevariable light transmission/absorption system type or of the variablelight diffusion system type or of the photochromic type. This glazingadditionally includes at least one means of thermal protection for theelectrically controllable system and/or of adjustment of the opticalappearance imparted to the glazing by the electrically controllablesystem. This means is advantageously in the form of at least one coatingwith reflective properties in the infrared and/or in the visible and/orin the ultraviolet.

Depending on its configuration in the glazing, this reflecting coatingcan, in fact, assume two functions alternatively or cumulatively.

When the coating is placed in the glazing so that, once the glazing isfitted, it is between a source of heat and the active (electrochemical)system, it acts as a thermal screen, reflecting all or part of theenergy emitted by the source of heat. It thus prevents an excessiveheating of the active system of the electrochemical type. The mostadvantageous application relates to glazings fitted externally tobuildings or vehicles and intended to be exposed to long periods ofsunshine. It relates very particularly to electrochromic glazings which,in the colored state and in the absence of heat “filter”, can be heatedstrongly by energy absorption, the heating being detrimental to thelifetime of the glazing and even because of safety problems, it beingpossible for the surface temperature of the glazing to reach 80° C.without a heat filter.

It also relates to the active glazings of the photochromic type which,as mentioned above, tend to lose their properties in the event ofexcessive heating.

This has two very advantageous consequences:

on the one hand, the invention makes it possible to lengthen thelifetime of the “intelligent” glazings which were already intended forexternal applications. This is commercially and technically highlyadvantageous, both in the field of building construction, where thebuilders must guarantee lifetimes of the materials employed of at least5 or 10 years, and in the motor vehicle sector, where strict safetystandards apply, especially in terms of optical quality;

on the other hand, the invention makes it possible to envisage“intelligent” glazings for external applications, hitherto employedessentially internally for reasons of excessively poor thermaldurability, and/or of instability towards certain radiations, which is,for example, the case with some liquid-crystal glazings employingdichroic dyes which are relatively unstable to ultraviolet radiations.

A very advantageous optical function can also be imparted to thereflecting coating according to the invention by selecting it so that itmodulates the optical appearance and hence the aesthetics of theglazing. Two highly advantageous types of optical modulations can bethought of, no limitation being implied.

In the case of glazings with variable light transmission/absorption ofthe electrochromic type, it has already been seen above that the type ofelectrochemical system chosen makes it possible to set the limitsbetween which the light transmission or absorption of the glazing wouldbe able to vary. The same applies to the choice of the calorimetricappearance of the glazing. Thus the choice of an electrochromic systememploying tungsten oxide as cathodic electrochromic material will resultin a glazing whose color will be in the blue region.

Combining with such a system a reflecting coating whose opticalproperties can be adjusted precisely, especially through the choice ofits composition and of its thickness, allows the optical appearance ofthe glazing to be adapted in various ways: by appropriately selectingthe reflecting coating, the light transmission range of the glazing canbe lowered in a controlled manner without appreciably decreasing itscontrast (the contrast being defined as the ratio of the lighttransmission in the completely faded state to that in the completelycolored state). In addition, the reflecting coating may have acalorimetric impact on the glazing by modifying its color on either ofits faces.

These remarks also apply to the active glazings of the photochromictype: the reflecting coating limits their heating and hence preservestheir properties, and can also modulate their optical properties.

Furthermore, the reflecting coating can also be very advantageous whereaesthetics are concerned when it is incorporated into a glazing withvariable light diffusion of the liquid-crystal type. With glazing ofthis type an absolutely “symmetric” appearance is generally obtainedregardless of the side on which the viewer is placed, a transparentappearance in the nondiffusing state and an appearance which is often inthe milky white region in the diffusing state, which is the case withthe glazings currently marketed under the name of “Priva-lite” bySaint-Gobain Vitrage. However, for special applications it is nowdesired to obtain the ability of having a different optical appearancedepending on the side where the viewer is placed. The reflecting coatingaccording to the invention makes it possible to obtain this result,since a glazing provided both with the variable light diffusion systemand with the reflecting coating exhibits, especially in the diffusingstate, a face which will retain the white and milky diffusingappearance, referred to above, as well as an opposite face which, forits part, will have a reflecting appearance that can be modulated incolor and intensity by virtue of this coating. Glazing of this type madeoptically “disymmetric” advantageously finds application, for example,as glazing for a motor vehicle, such as a car roof; from the outside theviewer sees a particularly aesthetic reflecting glazing, whereas fromthe inside of the compartment the diffusing effect sought after ismaintained.

The reflecting coating can be given another function: by appropriatelychoosing its nature and its thickness it is possible to employ it as anelectrically conductive layer of the electrically controllable system.

Many reflecting coatings may be advantageously employed within the scopeof the invention. They may be single-layer coatings or may consist of astack of at least two layers. In general a reflecting layer is involved,which is used in combination with at least one layer of dielectricmaterial intended to protect it from chemical or mechanical attackand/or to adjust its optical properties. A coating is usually employedin the form of at least one reflecting layer placed between two layers(or superpositions of layers) of dielectric material of the metal orsilicon oxide or nitride type.

The reflecting layer may be chosen based on at least one of the metalsbelonging to the following group: silver Ag, gold Au, copper Cu,aluminum Al, chromium Cr, nickel Ni, iron Fe, tantalum Ta, zirconium Zr,zinc Zn, tin Sn, indium In, rhodium Rh, cadmium Cd or silicon Si (itbeing possible for these metals or metal alloys to be additionallynitrided).

It may also be a reflecting coating based on at least one metal nitridesuch as titanium nitride TiN, zirconium nitride ZrN or hafnium nitrideHfN.

Reflecting coatings meeting this definition and particularly preferredwithin the scope of the invention are layers based on silver, especiallyincorporated in a stack of the type:

dielectric/silver/dielectric or

dielectric/silver/dielectric/silver/dielectric, optionally with, betweenthe silver layer and at least one of the adjacent layers of dielectric,thin layers based on partially or completely oxidized metal, intended toact as nucleation layers and/or barrier layers, especially againstoxidation.

For further details, reference will be advantageously made especially toPatents EP-506 507, EP-611,213, EP 636,587, EP-638,528, EP-648,342,EP-678,484, EP-709,349 and EP-718,250, the entire contents of each arehereby incorporated by reference.

Another preferred reflecting layer glazing according to the inventionmeeting this definition is a layer based on Ni—Cr alloy or based onNi—Cr—Fe alloy of the steel type, alloys which are optionally nitrided,or based on tantalum. This layer is placed between two layers of oxideor nitride of the Ta₂O₅, SnO₂, TiO₂ or TiN type, as is describedespecially in Patent EP-511, 901, the entire contents of which is herebyincorporated by reference.

It may also be a layer based on TiN, used in combination with at leastone other layer of oxide of the TiO₂ or SiO_(x)C_(y) type, as isdescribed especially in Patents EP-638,527 and EP-20 650,938, the entirecontents of each being hereby incorporated by reference.

A description of a reflecting layer based on silicon used in combinationwith a second layer of oxide will also be found in Patent FR-2 391 173,the entire contents of which is hereby incorporated by reference.

Also included as another type of reflecting layer are the layers basedon optionally doped metal oxide(s), especially based on titanium oxide,like the coating of the glazings marketed under the name “Antelio” bySaint-Gobain Vitrage, or based on fluorine-doped tin oxide SnO₂:F or ontin-doped indium oxide ITO. For further details reference may be made,in particular, to Patent FR-2 310 977 for the description of the methodof preparation of a titanium oxide layer, or to Patents EP-544 577,EP-573 325 and EP-648 196 corresponding to PCT Application WO 94-25 410for the description of stacks of layers incorporating an SnO₂:F layer,the entire contents of each of which being incorporated by reference.Moreover, it may be noted that if a reflecting layer is chosen based ontitanium oxide which is at least partially crystallized in anatase oranatase/rutile form, this type of layer also has properties which are atthe same time photocatalytic and hydrophilic, which give it particularlyadvantageous antimist and/or antisoiling properties if it is depositedon one of the external faces of the glazing. Reference may be madeadvantageously to Patent FR 95/10 839 filed on Sep. 15, 1995 the entirecontents of which are hereby incorporated by reference, for furtherdetails.

Once the choice of the material of the reflecting layer has been made,its thickness may then be optimized as a function of the desired effect,especially as a function of the degree of “filtration” of the solarradiations which is required or of the modification of opticalappearance which in sought after.

The invention applies to various types of active glazings, of theelectrochemical type or of the photochromic type. As already seen, itmay involve glazings with variable light transmission/absorption,especially with a viologen or electrochromic system, especially of thetype of those described in the abovementioned Patents EP-0 338 876, EP-0408 427, EP-0 575 203 and EP-0 628 849, the entire contents of which arehereby incorporated by reference. It is preferably in the form of astack of functional layers including successively a preferablytransparent electrically conductive layer, a so-called cathodicelectrochromic layer capable of reversibly inserting cations such as H⁺,Li⁺, Na⁺, and Ag⁺, an electrolyte layer, optionally a counterelectrodein the form of a second so-called anodic electrochromic layer alsocapable of reversibly inserting cations and, finally, a secondelectrically conductive layer.

Insofar as the nature of the electrically conductive layers of thedevice is concerned, there are two possible alternative forms: it ispossible to use materials based on doped metal oxide, such at fluorinedoped tin oxide SnO₂:F or tin-doped indium oxide ITO. It is alsopossible to employ layers of metal or metal alloy, for example of goldAu, of silver Ag or of aluminum Al. As the device generally has twoelectrically conductive layers, they may either both be metallic or bothbased on doped oxide, or one metal-based and the otherdoped-oxide-based.

To form the layer of cathodic electrochromic material it is possible tochoose a material or a mixture of materials chosen from the groupincluding tungsten oxide WO₃, molybdenum oxide MoO₃, vanadium oxideV₂O₅, niobium oxide Nb2O5, titanium oxide TiO₂ a “cermet” material(combination of metallic and ceramic material, especially in the form ofmetal particles in a ceramic matrix) such as WO₃/Au or WO₃/Ag, or amixture of tungsten and rhenium oxides WO₃/ReO₃. These materials areespecially suitable in the case of reversible insertion of lithium ions.In the case where the device operates by reversible proton insertion,the same materials may be employed, but this time hydrated.

To form the layer of anodic electrochromic material, a material may bechosen which corresponds to the formula M_(x)A_(y)U_(z), with M atransition metal, A the ion employed for reversible insertion, forexample an alkali metal or a proton, and U a chalcogen such as oxygen orsulphur.

Especially in the case of an insertion of proton ions H⁺, it may be acompound or a mixture of compounds belonging to the group includingLiNiO_(x), IrO_(x), H_(y), IrO_(x)H_(y)N_(x), NiO_(x),NiO_(x)H_(y)N_(x), RhO_(x), CoO_(x), and MnO_(x). In the case of areversible insertion of lithium ions Li⁺, a compound or a mixture ofcompounds belonging to the group including LiNiO_(x), LiMn₂O₄, IrO_(x),Li_(x)IrO_(y), NiO_(x), CeO_(x), TiO_(x), CeO_(x)—TiO_(x), RhO_(x),CoO_(x), CRO_(x) and MnO_(x) is preferably chosen.

In the formulas above, x, y, and z are not particularly limited, and mayeach independently be zero, any integer, or fractional value.

Insofar as the choice of the electrolyte material is concerned, thereare in fact two types, as has already been mentioned above.

It may be a layer of aqueous liquid such as water containing addedsulphuric or phosphoric acid in the case of a reversible insertion ofprotons, or a layer of anhydrous liquid such as propylene carbonatecontaining a lithium salt in the case of a reversible insertion oflithium ions. It may also be a layer of gel or polymer, especiallyproton-conductive polymers of the type of solid solution of polyethyleneoxide and of phosphoric acid PEO—H₃PO₄ (in this case the polymer alsoconstitutes an electronic insulator) or else based on a polymer obtainedby copolymerization of three precursors including two types of graftedtrialkoxysilanes and a plasticizer containing at least one urea group.The lithium ion-conductive polymer chosen may be an ionomer obtained bypartial neutralization of polyacrylic acid or a polymer based onbranched polyethyleneimine and a lithium salt. The nature and thesynthesis of such polymeric products. is not particularly limited and isgenerally available in the patents cited in the preamble of the presentapplication.

However, it may also be an electrolyte in the form of a solid material,especially based on metal oxide. According to an alternative form of theinvention the system is chosen such that it contains only layers ofsolid material. In the context of the invention “solid material” isintended to mean any material which has the mechanical behavior of asolid, in particular any essentially inorganic or organic material orany hybrid material, that is to say partially inorganic and partiallyorganic, like the materials which can be obtained by sol-gel depositionfrom organo-inorganic precursors. A so-called “all-solid” systemconfiguration is then obtained which offers an advantage in terms ofease of manufacture. In fact, when the system contains an electrolyte inthe form of polymer which does not have the mechanical behavior of asolid, for example, this in fact makes it necessary to manufacture, inparallel, two “half cells”, each having a carrier substrate coated witha first electrically conductive layer and then with a secondelectrochemically active layer, these two half-cells being subsequentlyassembled by inserting the electrolyte between them. With an “all-solid”configuration the manufacture is simplified, since all of the layers ofthe system can be deposited, one after the other, on a single carriersubstrate. The electrochromic system/carrier substrate unit is thus madelighter, since it is then possible to be satisfied with a single carriersubstrate instead of two, as is usual.

In addition, whether the electrolyte is “solid” or not, it may include alayer of an ionically conductive material capable of inserting ionsreversibly, but the degree of oxidation of which is kept essentiallyconstant. It may be especially a material with electrochromicproperties, as described in the abovementioned Patent FR-96/03799, theentire contents of which are hereby incorporated by reference.

The system with variable light transmission/absorption of the componentaccording to the invention can thus be found placed either between tworigid substrates or on a rigid mingle substrate more particularly in thecase of an “all-solid” system. The rigid carrier substrates arepreferably made of glass, acrylic polymer, polycarbonate, orpolyurethane.

Regardless of the configuration adopted, provision may additionally bemade for laminating the carrier substrate or at least one of the carriersubstrates of the electrochromic system through the intermediacy of asheet of bonding polymer of the PVB (polyvinylbutyral), EVA(ethylene-vinyl acetate) or PU (polyurethane) type.

At least one of the carrier substrates may also be used in combinationwith another rigid substrate through the intermediacy of a gasinterlayer. The glazing then becomes a multiple glazing with reinforcedthermal insulation properties, especially a double glazing. Thislaminated structure may be fitted as insulating double glazing, thesequence then being, for example, glass 1/reflecting coating/sheet ofbonding polymer/glass 2/electrochromic system/glass 3/gasinterlayer/glass 4. (This multiple glazing configuration can also beadopted when the electrically controllable system is of theliquid-crystal type).

The reflecting coating is preferably placed on the face of one of thecarrier substrates which is opposite that facing the side of the active(electrochromic) system or on one of the faces of one of the othersubstrates of which the glazing consists. It is thus possible to have aglazing exhibiting the sequence:

glass 1/reflecting coating/sheet of bonding polymer/glass2/electrochromic system/glass 3. This reflecting coating mayalternatively be placed on the face of the glass 2 facing the sheet ofbonding polymer or on the external face of the glass 1 if it hassufficient mechanical and chemical durability. This laminated structuremay be fitted as insulating double glazing, then, for example, with thesequence glass 1/reflecting coating/sheet of bonding polymer/glass2/electrochromic system/glass 3/gas interlayer/glass 4.

The glazing according to the invention may also be chosen with variablelight diffusion, especially by incorporating the so-called optical valveor liquid-crystal systems which were described above. In the case ofliquid-crystal systems the nature of the polymeric matrix and of thecrystals is judiciously chosen so that the ordinary index of the liquidcrystals n_(o) is equal to the index of the polymer n_(p).

Regardless of whether optical valves or liquid-crystal systems areinvolved, both the systems are in the form of a polymer-based compositefilm. In order to ensure its electrical supply it is usually placedbetween two electrically conductive layers, especially transparent onesand of the type of those employed for the electrochromic systemsdescribed above.

It should be noted, furthermore, that the droplets of liquid crystals ofthe polymer-liquid crystal composite may also contain a dye or a mixtureof dyes, especially in the form of dichroic dyes, which are dyesexhibiting an absorption anisotropy which can be oriented by the liquidcrystals.

In addition, the film with its two conductive layers is usually providedon at least one of its faces, and preferably on each of them, with acarrier substrate. The latter is generally transparent. It may be chosento be rigid or semirigid, for example may be made of glass, acrylicpolymer of the polymethyl methacrylate PMMA type or of polycarbonate PC.It may also be flexible, especially of polyethylene terephthalate PET orbased on some flexible polycarbonates. It may thus have a structure ofthe PET/ITO/polymer-liquid crystal composite/ITO/PET type, which is inthe form of a flexible sheet which can be handled with ease. This unit(composite+electroconductive layers+at least one carrier substrate) canbe subsequently laminated to at least one transparent rigid substrate ofthe glass type with the aid of at least one layer of bonding organicpolymer of the polyvinylbutyral PVB or ethylene-vinyl acetate EVA typeor polyurethane PU.

According to a preferred configuration of this type of glazing withvariable light diffusion the reflecting coating according to theinvention is placed on the face of one of the carrier substrates facingthe side of the system with liquid crystals. However, it may also beplaced on the opposite face or on one of the faces of one of the othersubstrates of which the glazing consists. The glazing can thus have thesequence:

glass (1) /reflecting coating/sheet of bonding polymer/sheet of flexiblepolymer/liquid-crystal system/sheet of flexible polymer/sheet of bondingpolymer/glass (2). As in the case of the electrochromic glazing, thereflecting coating may alternatively be situated especially on theexternal face of the glass 1.

Regardless of whether an electrically controllable system of theelectrochromic type or of the liquid-crystal type is involved, adouble-glazing configuration may be chosen such that the carriersubstrate(s) of the electrically controllable system is (are) separatedfrom the substrate provided with the reflecting coating according to theinvention by a gas interlayer. There is then a glazing of the type:

glass 1/reflecting coating/gas interlayer/electrically controllablesystem used in combination with at least one glass 2.

Whatever the type of electrically controllable glazing envisaged, it maybe desired to give it an additional property of decreasing its lightand/or energy transmission with a view to proposing a glazing exhibitingenhanced antisunshine properties or else improved visual comfort, anantidazzle effect or given colorimetric appearance In this case at leastone of the substrates of the glazing may be chosen to be absorbent wherelight and/or energy is/are concerned, especially in the form of asubstrate which is tinted in bulk in a more or less pronounced manner.If the reflecting coating is employed for protection of the electricallycontrollable system against solar radiation, it is, of course,preferable to configure the glazing so that the substrate which istinted in bulk is separated from the substrate in contact with thereflecting coating by at least the electrically controllable system, forexample with a sequence of the type:

clear glass 1/reflecting coating/ . . . /electrically controllablesystem of the liquid-crystal type/ . . . /tinted glass 3, the dotsrepresenting at least one material of the rigid substrate, sheet ofbonding polymer or gas interlayer type.

By fitting the glazing in a building or a vehicle so that in it theclear glass faces outwards, the electrically controllable system incontact with an absorbent glass is prevented from being heated:

when the electrically controllable system has variable absorption, as isthe case with an electrochromic system, it is, in fact, liable to beheated by strong sunshine via an energy absorption phenomenon when it isin the colored state. and hence the advantage of the reflecting coatingaccording to the invention (the same comment applies to thephotochromes); and/or

when the electrically controllable system is of the liquid-crystal typeor when it is a system with variable absorption of the electrochromictype which is in the faded state, it is better to avoid it being incontact with a tinted glass subjected directly to sunshine, to avoid itsbecoming heated by this contact, even if it is not absorbent itself.

Glazings which are tinted in bulk and especially suited to buildingconstruction, are, for example, marketed under the name “Parsol” by thecompany Saint-Gobain Vitrage. Other types of glass with reduced energytransmission are also advantageous within the scope of the presentinvention:

These are especially glasses of bronze color, as described in U.S. Pat.No. 4,190,542 and U.S. Pat. No. 4,101,705, the entire contents of whichare hereby incorporated by reference, or glasses whose composition hasbeen adjusted mainly with a view to a motor vehicle glazing application.They are, for example, glasses called TSA* or TSA**, in which thecontents of coloring oxides of the Fe₂O₃, FeO and CoO type are adjustedin order to have a selectivity defined by the ratio T_(L)/T_(E) of atleast 1.30 or even 1.40 to 1.50, and a tint in the green region.Reference will be made advantageously for further details to EuropeanPatent Application EP-A-0 616 883, the entire contents of which arehereby incorporated by reference. The content of the abovementionedcoloring oxides in the glass compositions according to the teaching ofthis patent will be recalled briefly below (weight proportions).

According to a first series:

Fe₂O₃ 0.55 to 0.62% FeO 0.11 to 0.16% CoO 0 to 12 ppm, especially < 12ppm especially with the Fe²+/Fe ratio of about 0.19 to 0.25.

According to a second series;

Fe₂O₃ 0.75 to 0.90% FeO 0.15 to 0.22% CoO 0 to 17 ppm, especially < 10ppm especially with the Fe₂+/Fe ratio of about 0.20.

They may also be glasses tinted in bulk, especially in the blue-greenregion, such as those described in Patent Application EP-A-0 644 164,the entire contents are hereby incorporated by reference, thecomposition of which is recalled below:

SiO₂ 64 to 75% Al₂O₃ 0 to 5% B₂O₃ 0 to 5% CaO  2 to 15% MgO  0 to 15%Na₂O  9 to 18% K₂O 0 to 5% Fe₂O₃ 0.75 to 1.4%  (total iron expressed inthis form) FeO 0.25 to 0.32% SO₃ 0.10 to 0.35%

They may also be glasses such as those described in PCT Applicationfiled under number PCVT/FR95/00828 on Jun. 22, 1995, corresponding toApplication FR-A-2 721 599, the entire contents of each which are herebyincorporated by reference, the composition of which, still in weightpercentages, is recalled below:

SiO₂ 69 to 75% Al₂O₃ 0 to 3% B₂O₃ 0 to 5% CaO  2 to 10% MgO 0 to 2% Na₂O 9 to 17% K₂O 0 to 8% Fe₂O₃ (total iron) 0.2 to 4%   Se, CoO, Cr₂O₃,NiO, CuO   0 to 0.45%

The content of coloring agents other than iron being at least equal to0.0002% when the Fe₂O₃ content is equal to or lower than 1.5%, it beingpossible for this composition also to contain fluorine, zinc, zirconium,cerium and titanium oxides and less than 4% of barium oxide, the sum ofthe percentages of the alkaline-earth metal oxides remaining equal to orlower than 10%.

Still according to the teaching of this patent, it is preferred that thecoloring agents other than iron should be introduced into the glasscomposition by themselves or in combination, according to weightcontents which preferably remain lower than the following limits:

Se < 0.008% CoO < 0.04% Cr₂O₃ < 0.1% NiO < 0.07% CuO < 0.03%.

They may also be glasses such as those described in ApplicationPCT/FR96/00394 filed on Mar. 14, 1996 and corresponding to the FrenchPatent Application filed on Mar. 16, 1995 under number 95/03858, theentire contents of each are hereby incorporated by reference, glassesincluding, expressed in weight percentages, from 0.85 to 2% of totaliron expressed in the Fe₂O₃ form, the weight content of FeO beingbetween 0.21 and 0.40%.

According to this patent the compositions are, according to a firstseries, the following:

SiO₂ 64 to 75% Al₂O₃ 0 to 5% B₂O₃ 0 to 5% CaO  2 to 15% MgO 0 to 5% Na₂O 9 to 18% K₂O 0 to 5% Fe₂O₃ (total iron expressed in this form) 0.85 to2%   FeO 0.21 to 0.40% CoO, Cr₂O₃, Se, TiO₂,   0 to 0.04% MnO, NiO, CuOSO₃ 0.08 to 0.35%

and, according to a second series, the following:

SiO₂ 68 to 75% Al₂O₃ 0 to 3% B₂O₃ 0 to 5% CaO  2 to 10% MgO 0 to 2% Na₂O 9 to 18% Fe₂O₃ (total iron expressed in this form) 0.95 to 2%   CoO,Cr₂O₃, Se, TiO₂,   0 to 0.04% MnO, NiO, Cuo FeO 0.29 to 0.40% SO₃ 0.08to 0.35%

It may also be a glass tinted in accordance with the teaching of PatentEP-0 452 207, the entire contents of which are hereby incorporated byreference, the composition of which is generally the following, inweight proportions:

SiO₂ 64 to 75% Al₂O₃ 0 to 5% B₂O₃ 0 to 5% CaO  5 to 15% MgO 0 to 5% Na₂O10 to 18% K₂O 0 to 5%

the sum of the alkaline-earth metal oxides being between 6 and 16% andthose of the alkali metal oxides between 10 and 20% and including, ascoloring agents:

Fe₂O₃ (total iron): 1.4 to 4% CoO   0 to 0.05%

with CoO>approximately 0.02% when Fe₂O₃<approximately 2%, as well asoptionally selenium and chromium oxide, it being possible for the sumCoO+Se+Cr₂O₃ to reach 0.24%, this glass having an overall lighttransmission factor under illuminant A (LT_(A)) equal to or lower thanapproximately 20% and an overall energy transmission factor (T_(E))lower than or equal to approximately 12% at a thickness of 3.85 mm.

There may also be mentioned the tinted glasses whose compositioncorresponds to that defined in Patent WO 93/07095, the entire contentsof which are hereby incorporated by reference, in the following manner,still in weight proportions:

SiO₂ 64 to 75% Al₂O₃ 0 to 5% B₂O₃ 0 to 5% CaO  5 to 15% MgO 0 to 5% Na₂O10 to 18% K₂O 0 to 5% and, as coloring agents: Fe₂O₃ (total iron) 0.45to 2.5%  CoO 0.001 to 0.02%  Se    0 to 0.0025% Cr₂O₃   0 to 0.1%

such a glass having an overall energy transmission factor (T_(E)) lowerthan the light transmission factor under illuminant A (LT_(A)), thefactor T_(E) being between 10 and 48% and the factor LTA between 20 and60% at a thickness of 3.85 millimeters.

All these types of tinted glass compositions can therefore beadvantageously chosen so that the glazings have energy transmissionvalues of between 6 and 70%, preferably between 20 and 60% and lighttransmission values of between 10 and 85%, preferably 20 and 75%. Theseranges include all values and subranges therebetween.

Another subject-matter of the invention is the use of the glazingsdescribed above as glazings for building construction, especially asexternal glazings, internal partition glazings or glazed doors and asglazings fitted to means of transport, especially motor vehicle glazingssuch as car roofs, railway glazings or aircraft glazings, especially aswindscreens windscreen sunshade strips.

These glazings may have a “monolithic” structure, that is to say with asingle rigid substrate, or a plurality of rigid substrates, may have alaminated and/or multiple glazing structure, or else a so-calledasymmetric glazing structure with an external plastic layer, basedespecially on polyurethane with energy-absorption properties, astructure described especially in Patents EP-191 666, EP-190 953, EP-241337, EP-344 045, EP-402 212, EP-430 769 and EP-673 757, the entirecontents of each of which are hereby incorporated by reference.

The glazings of the invention can also be employed as mirrors, byadjusting the nature and the thickness of the reflecting coating, andmore particularly as unsilvered mirrors which can also be described as“spy mirrors”. If the silvering of the mirror is replaced with avariable light diffusion system of the liquid-crystal type, not only cana viewer in a room observe the interior of an adjacent room without anyperson present in this adjacent room being aware of this, but inaddition the viewer can, if he or she desires, prevent a person enteringthe room where they find themselves from realizing that it is anunsilvered mirror, by making the glazing diffusing.

BRIEF DESCRIPTION OF DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings, wherein:

FIG. 1: an electrochromic glazing with laminated structure in section,

FIG. 2: an electrochromic glazing according to FIG. 1 fitted as doubleglazing,

FIG. 3: an electrochromic glazing fitted as double glazing according toanother configuration,

FIG. 4: a liquid-crystal glazing in section,

FIG. 5: a liquid-crystal glazing fitted as double glazing.

These figures are extremely diagrammatic and do not conform to theproportions of the various components shown, to make them easier toread. In particular, the electrical connections which are generallyknown in the art are not shown.

EXAMPLES

Having generally described this invention, a further understanding canbe obtained by reference to certain specific examples which are providedherein for purposes of illustration only and are not intended to belimiting unless otherwise specified.

The rigid substrates employed for all the following examples aresubstrates made of silica-soda-lime glass of 4 mm thickness. (Theirthickness can in fact be preferably chosen within the range of 3 to 6mm).

The so-called “clear” glass substrates are glasses marketed bySaint-Gobain Vitrage under the name Planilux. The so-called “tinted”glass substrates are glasses exhibiting, at approximately 4 mmthickness, values of T_(L) of 35% and of T_(E) of 18.7% under illuminantD₆₅. Their chemical composition is defined by that of Example 2 of theabovementioned Patent WO 93/07095, the entire contents of which areincorporated by reference, which includes, in proportion by weight, thefollowing oxides affecting the color:

Fe₂O₃ (total iron): 1.65% Co 0.00110%

Example 1

FIG. 1 shows an electrochromic glazing of laminated structure containingthree glasses in a configuration adapted, for example, to use as a carroof: two clear glasses 2, 3 are shown, between which is placed anelectrochromic system 4 consisting of the stack of the followingfunctional layers (stack in accordance with the teaching of EP-0 628849, the contents of which are hereby incorporated by reference):

a 300 nm first electroconducive layer of SnO₂:F,

a 55 nm first layer of anodic electrochromic material made of hydratediridium oxide (it could preferably be replaced with a layer of hydratednickel oxide).

a 70 nm layer of hydrated tantalum oxide (Ta₂O₅.H_(x)), its functionbeing protection.

a layer of electrolyte as solid solution of polyethylene oxide withphosphoric acid (PEO—H₃PO₄), of 100 micrometers,

a 350 nm second layer of cathodic electrochromic material based ontungsten oxide,

a 300 nm second layer of SnO₂:F.

The glass 2+electrochromic system 4+glass 3 unit is next laminated witha third clear glass 1 through the intermediacy of a sheet 5 of organicbonding polymer of the PVB type from 0.5 to 1 mm in thickness,especially 0.75 mm. On the face of the glass 1 facing the side of thePVB sheet 5 is placed a reflecting coating 6 consisting of the stack ofthe following thin layers, starting from glass 1:

a 41 nm layer of SnO₂,

an 18 nm first layer of silver,

a 74 nm layer of SnO₂.

a 12 nm second layer of silver,

a 33 nm layer of SnO₂.

In addition, on both sides of each of the silver layers is placed a thinmetal layer based on NiCr, of approximately 0.5 to 1.5 nm.

This type of stack is, in a conventional manner, obtained by a magneticfield-assisted cathode sputtering technique, the Ni—Cr layers making itpossible to protect the silver layers from oxidation during thedeposition of SnO₂ layers by reactive sputtering in the presence ofoxygen, being partially or completely oxidized in their place.

For other types of equivalent stacking of the (dielectric/silver)_(n)type, with n≧1, reference will be advantageously made to the patentscited previously. (Thus, dielectric materials other than tin oxide maybe employed, for example TiO₂, ZnO, Nb, Ta₂O₅, Si₃N₄, etc. or asuperposition of dielectric materials like SnO₂/Nb₂O₅, Nb₂O₅/ZnO,SnO₂/Ta₂O₅, Similarly, the Ni—Cr barrier layers are optional and can besubstituted, for example, with layers of metal of the Ti, Ta, Nb, Zn, Snand similar type).

The above glazing is preferably fitted so that the glass 1 facesoutwards to the atmosphere. The electrochromic system 4 is thusprotected from solar radiation both by the PVB sheet 4 which,preferably, contains agents that filter out the ultraviolet region, andabove all by the reflecting coating 5 according to the invention. Thiscoating, which resorts to two reflecting layers, is particularlyeffective in its function as a sunlight filter. This is proportionatelymore important when this glazing is employed as a car roof, that is tosay in a horizontal position, which is a configuration particularlystressing the electrochromic system in terms of temperature behavior, oreven in a position inclined in relation to the vertical, if theintention is to employ it as greenhouse glazing, roof window of theskylight type, etc.

Example 2

Example 2 corresponds to the electrochromic glazing configuration shownin FIG. 2: the glasses 1, 2, 3 of FIG. 1 are seen again, as is the namePVB sheet 5, the same reflecting coating 6 and the same electrochromicsystem 4. The three-glass unit has been fitted as double glazing withthe aid of a fourth clear glass 7 through the intermediacy of a layer ofargon 8, 12 mm in thickness, with the aid of means of assembly which areknown in the field of double glazing and are not shown.

On the face of the glass 7 facing the argon layer 8 is placed a coating9 with low-emissivity properties, of the type of those applied to theglazings marketed under the name of Planitherm by Saint-Gobain Vitrage,that is the following stack:

a 40 nm layer of tin oxide,

a 9 nm layer of silver,

a 40 nm layer of tin oxide, together with, as in the case of the stack 6described above, the presence of two thin layers of 0.5 to 1.5 nm ofNi—Cr, intended to protect the silver from oxidation. This type ofdouble glazing can be employed especially as external glazing fitted tobuilding facades (as described in Patent.EP-0 575 207, the entirecontents of which are hereby incorporated by reference) or ingreenhouses, verandas or roof windows.

This type of structure results in two advantages; from an aestheticpoint of view, when all the glazing of the facade is converted to thecolored state, the presence of the reflecting coating 6 gives thefacade, on the external side, an aesthetic reflecting appearance, whichmay be preferred to the relatively dark and absorbent appearance whichthin glazing would have when seen from the outside without thereflecting coating in question.

From the point of view of heat protection, the fitting according toFIGS. 1 and 2 protects the electrochromic glazing effectively againstexcessive heating.

The second coating of the low-emissive type 9 based on a layer of silver(which could, preferably alternatively be made of SnO₂:F, for example)does not contribute to the effect of protection against theelectrochromic system. It is optional, but its presence makes itpossible to improve the thermal insulation properties characteristic ofa double glazing structure, especially by reducing its coefficient K(the coefficient K represents the heat flow which passes through 1 m² ofwall with a temperature difference of 1 degree between the oppositesides of the wall, for example, the interior and the exterior of theroom).

The spectrophotometric values in the minimum colored state CS and in themaximum faded state FS are collated in Table 1 below for Examples and 2,with reference to the illuminant D₆₅: the light transmission T_(L), theenergy transmission T_(E), the energy absorption EA, in percentages, thecoefficient K in W m⁻²° K⁻¹, the solar factor SF defined by the ratio ofthe total energy entering the room through the glazing to the incidentsolar energy, dimensionless.

Also shown in the table are: an Example 2 bis, corresponding to theconfiguration of Example 2 but devoid of the low-emissive coating 9, andan Example 2ter which, by way of comparison, also corresponds to theconfiguration of Example 2, but is devoid of the reflecting coating 6according to the invention.

TABLE 1 Example 1 Example 2 Example 2BIS Example 2TER CE FE CE FE CE FECE FE T_(L) 10 48.4 8.5 41.5 9.1 44.2 10.2 50 T_(E) 4.9 25.2 4.0 19.84.4 22.2 5.3 29.2 EA 58.8 38.4 59.0 39.8 59.1 39.5 84.2 53.7 SF 0.200.36 0.08 0.25 0.12 0.28 0.11 0.37 K 5.6 5.6 1.4 1.4 2.6 2.6 1.4 1.4

From this table it is seen that the elimination of the low-emissivestack 9 in Example 2bis, compared with Example 2, increases the minimumvalue of T_(L) of the glazing by 3% without affecting its energyabsorption, but slightly to the cost of the coefficient K and of thesolar factor SF. The choice of any one of the configurations will dependon the intended application, the climate, etc.

When Examples 2 and 2ter are compared, it can also be seen that thepresence of the reflecting coating in Example 2 does not impair thecontrast and only very slightly impairs the light transmission of theglazing, but it makes it possible to reduce the energy absorption verysignificantly.

Furthermore, for each of the configurations of the Examples 1 and 2, themaximum surface temperature of the glazings was measured in comparisonwith identical glazings devoid of the protective coating 6; when thelatter are subjected, in horizontal position, to an exposure to sunlightcorresponding to an energy of 850 W/m², it is found that the maximumtemperature of the glazings according to Examples 1 and 2, in thecolored state, is at most 69° C., whereas it is 83° C. in the absence ofcoating 5. This difference of 14° C. is far from insignificant, becauseit allows the lifetime of the electrochromic glazings to be increased.

It should be noted, furthermore, that if an “all-solid” electrochromicsystem 4 is chosen, it is possible to have a “lighter” double glazingstructure than that shown in FIG. 2, especially of the glass1/electrochromic system/gas layer/glass 2 type; the reflecting coatingcan then be placed on the external face of the glass 1, if it has therequired durability, for example, if it is TiO₂ based, similar to thecoating with which glazings marketed under the name of Antélio bySaint-Gobain Vitrage are provided.

Example 3

Example 3 corresponds to the configuration of FIG. 3, which shows anelectrochromic double glazing which has the same components (but isdevoid of the low-emissive stack 9) as that in FIG. 2, assembleddifferently.

Glass 1, which faces outwards once the glazing is fitted, carries onlythe reflecting coating 6 and is not laminated. The electrochromic system4 is therefore between the glasses 7 and 3, the glass 3 being laminatedto glass 2 through the intermediacy of the PVB sheet 5. The unit of theglasses 2, 3 and 7 is next fitted as double glazing via an argon layer 8with the glass 1 carrying the reflecting coating 6 on its face facingthe argon layer.

Many other alternative forms of electrochromic glazings in accordancewith the invention are possible, as already mentioned above. It is thuspossible to have the configuration of Example 3, but eliminating theglass 2 and the PVB sheet 5, thus avoiding laminating glass 3.

If an “all-solid” electrochromic system 4 is adopted, for exampleexhibiting the following stack:

a 300 nm electrically conductive layer of SnO₂:F,

a 380 nm layer of cathodic electrochromic material made of tungstenoxide,

a double layer electrolyte made up of an 18 nm layer of hydratedtantalum oxide

Ta₂O₅ nH₂O and a 200 nm layer of hydrated tungsten oxide WO₃ nH₂O,

a 45 nm layer of anodic electrochromic material based on hydratediridium oxide

H_(x)IrOy (it can preferably be replaced with hydrated nickel oxide),

a 200 nm electrically conductive layer of ITO,

then it is possible to have a double glazing structure with only twoglasses, of the glass 1/reflecting coating 6/gas layer 8/electrochromicsystem 4/glass 2 type.

The following Examples 4 and 6 refer to a liquid-crystal glazing.

Example 4

Example 4 refers to a liquid-crystal glazing as shown in FIG. 4:

It includes two clear glasses 10, 11, between which are placed two 0.75mm sheets of PVB 12, 13, surrounding two sheets of polyethyleneterephthalate PET 14, 15, 175 micrometers in thickness, between which isthe liquid-crystal system 16, 25 micrometers in thickness. In fact, themanufacture is done in two steps, firstly the manufacture of thePET/ITO/polymer-liquid crystal composite/ITO/PET film, a film which isnext laminated to the glasses 10 and 11 with the aid of the sheets 12and 13.

In addition, between the glass 11 and the PVB sheet 13 there is areflecting coating 17 similar to the reflecting coating 5 with twolayers of silver, but with different thicknesses of silver layers, thestack 17 is as follows (in accordance with the teaching of the EuropeanPatent EP-638 528, the entire contents of which are hereby incorporatedby reference):

a 34.4 nm layer of SnO₂,

a 12 nm first layer of silver.

a 98 nm layer of SnO₂,

an 18 nm second layer of silver,

a 35 nm layer of SnO₂.

In addition, on each side of each of silver layers in placed a thinmetal layer of approximately 1.5 nm of Nb.

The liquid-crystal system 16 comprises two transparent conducting layersof ITO of resistivity 100 ohms per square, deposited on each of the PETsheets, between which is a transparent polymer-liquid crystal compositeconsisting of a polymer in which microdrops of nematic liquid crystalshave been dispersed beforehand, which forms the liquid-crystal emulsion.The liquid-crystal system employed is of the type of those described inPatents WO-90/03593, U.S. Pat. No. 5,206,747 and EP-0 409 442, theentire contents of which are hereby incorporated by reference, andmarketed by Saint-Gobain Vitrage under the name Priva-lite. It operatesat the voltage of 110 V/50 Hz: when supplied with electricity it istransparent. It becomes diffusing when the electrical supply is cut off.It should be noted that if dichroic dyes are introduced into thedroplets of liquid crystals, the coating 17 serves at least partially asan ultraviolet filter protecting them. This ultraviolet effect can bereinforced by employing, on the outside, a glass with ananti-ultraviolet filter effect.

Example 5

Example 5 also relates to a liquid-crystal glazing of the type shown inFIG. 4, with the same PET/ITO/polymer-liquid crystal composite/PET/ITOliquid-crystal system 14, 15, 16 and the same reflecting coating 17.Here, on the other hand, the glare 11 is only 2 mm in thickness and thesecond glass 10 is a glass tinted in bulk as defined above, 4 mm inthickness. In addition, the PVB sheets 12, 13 are replaced with 0.65 mmsheets made of polyurethane.

The following photometric values, still under the illuminant D₆₅ andwith reference to ISO standard 9050 are collated in the Tables 3 and 4below, for Examples 4 and 5 respectively: T_(L) the light transmissionin %, lambdadom (T) the dominant transmission wavelength in nm, pe (T)the transmitted color purity in %, T_(E) the energy transmission in %,the substrate 11 “side” light reflection R_(L), and its dominantwavelength and its purity lambda dom (R_(L)) and pe (R_(L)), thesubstrate 10 “side” light reflection R′_(L), and its dominant wavelengthand its purity lambda dom R′_(L)) and pe (R′_(L)). Also given are thesolar factors SF, already explained, as well as the values of energyabsorption EA and of haze H, defined by the light diffusion ratio in %.All these data are shown in the “ON” state, that is, in the transparentstate when the glazing is supplied with electricity, and in the “OFF”state, that is to say when the glazing is no longer supplied withelectricity and is diffusing.

TABLE 3 EXAMPLE 4 “ON” “OFF” T_(L) 37.6 33.8 lambda dom (T) 571 559 pe(T) 18.17 9.15 R_(L) 15.45 14.8 lambda dom (R_(L)) 485 485 pe (R_(L))32.1 32.2 R′_(L) 22.5 20.65 lambda dom (R′_(L)) 480 480 pe (R′_(L)) 8.947.92 EA 48.75 52.3 SF 30.5 28.7 H <8 >97 T_(E) 19.03 16.02

By way of comparison, the spectrophotometric values of a glazing ofconfiguration identical with that of the glazing of Example 4 but devoidof the reflecting coating 17 according to the invention were measured:such a glazing has an R_(L) value identical with that of R′_(L) andequal to 18.4% in the “ON” state and to 16.5% in the “OFF” state.Similarly, the dominant wavelengths of the references R_(L) and R′_(L)are identical and equal to 491 nm, whether the glazing is in the “OFF”state or in the “ON” state. The purity values associated with thereflections R_(L) and R′_(L) are also identical, and equal to 5.2%whether the glazing is in the “OFF” state or in the “ON” state Its solarfactor SF is 67 in the “ON” state and 65 in the “OFF” state. Its lighttransmission is 73.5% in the “ON” state and 70.8% in the “OFF” state,associated with a dominant wavelength which in always equal to 569 nmand a purity which is always equal to 4.3-4.4%.

TABLE 4 EXAMPLE 5 “ON” “OFF” T_(L) 15.7 14.6 lambda dom (T) 528 525 pe(T) 8.9 8.7 R_(L) 16.0 16.3 lambda dom (R_(L)) 486 486 pe (R_(L)) 30.029.7 R′_(L) 7.8 7.2 lambda dom (R′_(L)) 490 491 pe (R′_(L)) 12.1 10.3 EA58.3 58.9 SF 22 21.5 H <8 >97 T_(E) 6 5.3

The following conclusions may be drawn from these data: the T_(L) andT_(E) level can be preferably adjusted through the choice of thesubstrates, glassy, clear or tinted. The reflecting coating 17 forms athermal screen, if necessary, for the liquid crystal system. Above all,it is now possible to obtain reflection appearances on the external side(glass 11) and internal side (glass 10) which are different, with, forexample, nearly 10% difference between the values of R_(L) and R′_(L),and a color purity in external reflection which is more than twice ashigh as in internal reflection; there is a clear reflecting effect, withan intense color in the blue or blue-green region when the glazing isviewed from the outside, an effect which is much less marked when theglazing is viewed from the inside. It has been possible to verify that,in the absence of a reflecting coating, the glazing has absolutelyidentical appearances in internal and external reflection, theappearance of the glazing in the “ON” state being white and milky oneach side.

Finally, from Table 4 it is seen that the use of tinted glass allows theinternal reflection value R′_(L) to be lowered.

With this type of glazing it is therefore possible to modulate its lightdiffusion so that a room or a compartment is protected from externalviewing. In addition, the external viewer will see the reflectingglazing with a pleasant tint, regardless of whether it is in thediffusing state or not, an aesthetic external appearance which is quitesought after at present.

The invention thus makes it possible to adjust calorimetrically theexternal reflection appearance of a liquid-crystal glazing, with a veryspecial advantage that when this type of glazing is fitted to vehicles,it is then possible to adjust the appearance of the glazing seen fromthe outside as a function, for example, of the color of the bodywork.

Example 6

Example 6 corresponds to FIG. 5, which shows a liquid-crystal glazing ofthe type of that in FIG. 4, this time fitted as double glazing: theglass 10/PVB 12/PET 14/liquid-crystal system 16/PET 15/PVB 13/glass 11laminated structure is found again, a structure which is laminated to athird clear glass 18 through the intermediacy of an argon layer 19 andcarrying, on the side of its face facing the argon layer, the reflectingcoating 17. Glass 18 is intended to face outwards once the glazing isfitted.

Furthermore, the glazings as described in all of the above examples canbe functionalized, for example by having, on external face(s), anantisoiling coating, for example of at least partially crystallizedTiO₂, as referred to above, or an antirain hydrophobic coating based onfluorinated silane polymer.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

This application is based on French Patent Application FR96/10344, filedAug. 22, 1996, the entire contents of which are hereby incorporated byreference.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:
 1. Aglazing, comprising: a) at least one activelayer; b) at least one reflecting coating on said active layer; c) twoelectrically conductive layers; d) two transparent substrates, at leastone of which is rigid; and e) a gas layer; wherein the active layercomprises at least one optically variable layer which is an electricallycontrollable system, which system is a variable light diffusion system,comprising a composite polymer film having embedded therein droplets ofliquid crystals, wherein the ordinary index of said liquid crystals,n_(o), is equal to the index of said polymer, n_(p); and wherein thevariable light diffusion system is placed between the two electricallyconductive layers, and said gas layer is placed between the twotransparent substrates.
 2. The glazing of claim 1, further comprising atleast one sheet of bonding polymer, at least one flexible sheet, and atleast one glass sheet as the transparent rigid substrate, bondedtogether in the sequence order: glass/reflecting coating/sheet ofbonding polymer/flexible sheet/composite/flexible sheet/sheet of bondingpolymer glass.
 3. The glazing of claim 1, wherein said variable lightdiffusion system comprises an optical valve.
 4. The glazing of claim 1,wherein said liquid crystals comprise cholesteric liquid crystals. 5.The glazing of claim 1, wherein said liquid crystals comprise apolymer-liquid crystal NCAP or PDLC composition.
 6. The glazing of claim1, wherein said liquid crystals comprise a dye or mixture of dyes. 7.The glazing of claim 6, wherein said mixture of dyes comprises dichroicdyes.
 8. The glazing of claim 1, wherein said at least one transparentrigid substrate is a sunroof on a vehicle.
 9. The glazing of claim 1,wherein said at least one rigid, transparent substrate is a glass sheetwhich exhibits a bronze color.
 10. The glazing of claim 1, wherein saidat least one rigid transparent substrate is a glass sheet whichcomprises coloring oxides comprising Fe₂O₃, FeO and CoO, a content ofwhich is adjusted to yield of selectivity defined by a ratio T_(L)/T_(E)of at least 1.30, and exhibiting a tint in the green region.
 11. Theglazing of claim 1, wherein said at least one transparent rigidsubstrate is an aircraft glazing.
 12. The glazing of claim 1, whereinsaid at least one transparent rigid substrate is a railway glazing. 13.A multiple glazing structure, which comprises the glazing of claim 1.14. The multiple glazing of claims 13, which is an external glazing in abuilding.
 15. The glazing of claim 1, wherein said at least onereflecting coating is an ultraviolet filter.
 16. The glazing of claim 1,wherein said at least one reflecting coating is a thermal screen. 17.The glazing of claim 1, wherein said at least one reflecting coating isconfigured to confer disymmetry to said glazing and further comprising aliquid crystal system.
 18. The glazing of claim 1, which furthercomprises at least one tinted glass.
 19. The glazing of claim 1, whichfurther comprises an anti-soiling coating on an external face thereof.